<?php

namespace app\common\library;

/*
 *    <li>-41001: encodingAesKey 非法</li>
 *    <li>-41003: aes 解密失败</li>
 *    <li>-41004: 解密后得到的buffer非法</li>
 *    <li>-41005: base64加密失败</li>
 *    <li>-41016: base64解密失败</li>
 */
class WxBizDataCrypt
{
    private $appid;
    private $sessionKey;

    private  $OK = 0;
    private  $IllegalAesKey = -41001;
    private  $IllegalIv = -41002;
    private  $IllegalBuffer = -41003;
    private  $DecodeBase64Error = -41004;
    /**
     * 构造函数
     * @param $sessionKey string 用户在小程序登录后获取的会话密钥
     * @param $appid string 小程序的appid
     */
    public function __construct( $appid, $sessionKey)
    {
        $this->sessionKey = $sessionKey;
        $this->appid = $appid;
    }


    /**
     * 检验数据的真实性，并且获取解密后的明文.
     * @param $encryptedData string 加密的用户数据
     * @param $iv string 与用户数据一同返回的初始向量
     *
     * @return int 成功0，失败返回对应的错误码
     */
    public function decryptData( $encryptedData, $iv )
    {
        if (strlen($this->sessionKey) != 24) {
            return $this->IllegalAesKey;
        }

        $aesKey=base64_decode($this->sessionKey);


        if (strlen($iv) != 24) {
            return $this->IllegalIv;
        }
        $aesIV=base64_decode($iv);

        $aesCipher=base64_decode($encryptedData);

        $result=openssl_decrypt( $aesCipher, "AES-128-CBC", $aesKey, 1, $aesIV);

        $dataObj=json_decode( $result );
        if( $dataObj  == NULL )
        {
            return $this->IllegalBuffer;
        }
        if( $dataObj->watermark->appid != $this->appid )
        {
            return $this->IllegalBuffer;
        }
        $result = objectToArray($dataObj);
        return $result;
    }

}

